Portable roadway warning device with high-density filler and absent rigid metal ballast inserts

ABSTRACT

A roadway warning device including a portable rumble strip that includes high-density filler material to achieve a desired overall density and roadway stability of the rumble strip such as for use in high-speed traffic conditions without the use of conventional rigid metal ballast inserts. In some embodiments, the filler is dispersed and embedded within a flexible polymer composite matrix of the rumble strip body. In some embodiments, the filler is in the form of discrete unbound pieces of material disposed within a cavity of the rumble strip body. In some embodiments, the filler is in the form of a frangible article disposed within the rumble strip body.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 63/152,493 filed Feb. 23, 2021, which is hereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to a portable roadway warning device including one or more portable rumble strips to alert an operator of vehicle of an approaching condition, and more particularly to a portable roadway warning device having a portable rumble strip that provides a desired weight and road stability of the rumble strip without the use of conventional rigid metal ballast inserts.

BACKGROUND

Rumble strips are commonly used on roadways to provide a perceptible noise and physical warning vibration to an operator of a vehicle when the vehicle drives over the rumble strip. Rumble strips can be used to slow traffic or warn vehicle operators of an approaching condition, such as a work site, construction site, slow speed zone, checkpoint, and the like, without adversely affecting the stability of the vehicle.

Some types of rumble strips are intended to be permanently installed for long-term use, while others are intended to be temporary and portable for use at work zones and other applications of relatively short duration. Portable or temporary rumble strips generally should be reusable and quick and easy to deploy and remove. They also should have the ability to remain in place under the traffic conditions of their use, preferably without the use of adhesives or fasteners.

Some forms of portable rumble strips fabricated solely of polymeric materials may be suitable for use on roadways at the lower end of the vehicle traffic speed range, such as in parking lots, on residential streets, or the like. These lower-end rumble strips, however, do not have appropriate part density and weight to make them suitable for use at the higher end of the vehicle traffic speed range. Specifically, a lower-end rumble strip made solely of polymeric material typically will have a density below 0.05 pounds per cubic inch (1.38 g/cc), and thus will not produce sufficient pressure on the road surface for acceptable movement stability after encountering impacts from higher speed vehicles.

Rumble strips designed for service on roads and highways at the higher end of the vehicle traffic speed range also may be made with polymeric material, however these higher-end rumble strips often incorporate rigid metal ballast inserts within the polymer material to attain a heavier part density for enabling satisfactory movement stability against the greater impact forces of higher speed vehicles, such as those exceeding 50 miles per hour (80 kph). The rigid metal ballast inserts do not reinforce the physical durability of the base polymeric material of the rumble strip, rather the metal ballast inserts simply add weight to improve stability of the rumble strip during use.

SUMMARY

One problem with higher-end portable rumble strips that incorporate rigid metal ballast inserts is that the metal inserts are prone damage, such as by impact fracture, corrosion, or the like. The metal ballast inserts also typically are in the form of elongated rigid metal bars that can negatively affect the overall flexibility of the rumble strip design.

A unique portable rumble strip for a roadway warning device is described herein that uses high-density filler material to achieve a desired overall density and roadway stability that enables the rumble strip to be suitable for use in high-speed traffic conditions without the use of conventional rigid metal ballast inserts.

Generally, a portable rumble strip having an overall part density greater than 0.06 pounds per cubic inch (lb/in³), and more preferably about 0.08 lb/in³ or greater, provides acceptable road stability at highway vehicle speeds, such as those in the range of 50 to 80 mph, or greater. Accordingly, an exemplary portable rumble strip has high-density filler(s) dispersed in a polymeric matrix in an amount that achieves an overall part density greater than 0.06 lb/in³, such as in the range from 0.06 lb/in³ to 0.15 lb/in³.

According to an aspect, the portable rumble strip has an elongated flexible body that incorporates a composite with a flexible elastomeric matrix having the high-density filler material dispersed therein. The elongated flexible body including the flexible high-density composite may be a single unitary piece. Such a portable rumble strip may provide more complete flexibility in all directions, unlike conventional portable rumble strips that incorporate rigid housings or rigid metal bars into the rumble strip's geometric design. The increased flexibility provided by the elongated flexible body may include a flexible upper surface that absorbs impact from the vehicle, a flexible lower surface that conforms to the roadway surface, and a flexible middle/intermediate portion that facilitates the flexibility of the upper and lower surfaces. Co-vulcanization of distinct layers of the flexible body, if any, may improve overall flexibility and durability of the design.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having a flexible polymeric material matrix and at least one filler dispersed in the matrix that enhances the density of the composite, wherein the at least one filler is included in an amount that provides an overall density of the elongated flexible body in a range from 0.06 lb/in³ to 0.15 lb/in³.

In exemplary embodiments, the flexible polymeric material matrix of the composite may be co-vulcanized with the one or more additional portions of the flexible rumble strip body to form a unitary structure.

According to an aspect, the high-density filler material is dispersible and mixable in the polymer matrix material to enable the overall flexibility of the rumble strip body, while also being resistant to corrosion in a typical roadway condition. To enhance the overall density of the part, the high-density filler material has a density that is greater than the density of its surrounding polymeric matrix, and preferably has a specific gravity of at least 3.0 to enable a suitable volumetric loading in the polymeric matrix without significantly affecting the flexibility and performance of the rumble strip design.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having: a flexible elastomeric matrix, and at least one filler dispersed in the matrix, wherein: the at least one filler has a density greater than a density of the flexible elastomeric material matrix; the at least one filler has a specific gravity of 3.0 or greater; and the at least one filler is included in the composite in an amount that enhances the density of the composite, such that an overall density of the elongated flexible body is in a range from 0.06 lb/in3 to 0.15 lb/in3.

In exemplary embodiments, the composite and/or overall flexible body may be devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based filler material that is susceptible to corrosion from road salts.

In exemplary embodiments, the at least one high-density filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element, and more particularly such a material that is resistant to corrosion from road salts.

According to an aspect, the high-density filler material may be useful as a processing aid for the polymeric matrix material. For example, some high-density materials with a specific gravity of at least 3.0 may be used as an antidegradant, accelerator, coupling agent, or the like; and overloading of such a high-density material can be useful to achieve the desired overall part density for improving stability of the rumble strip at higher vehicle speeds.

According to an aspect, a portable rumble strip includes an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, wherein the portable rumble strip includes a composite having a polymeric material matrix and a filler dispersed in the matrix in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix, wherein the density of the filler is greater than a density of the polymeric material matrix.

In exemplary embodiments, the high-density filler includes zinc oxide (ZnO) in an amount between 500 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix of the composite, in which the ZnO also may be used as a processing aid for one or more polymers in the polymeric material matrix.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein the elongated body includes at least one cavity, and at least one filler in the form of discrete unbound pieces of material is disposed within the cavity.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein one or more frangible articles are disposed in the elongated body.

According to a general aspect, a portable rumble strip for placement on a roadway in a roadway warning system, includes filler material within a body of the rumble strip, the filler material being of a type and in an amount that increases the density of a rumble strip such that its mass can exert a pressure on the roadway to withstand impact from a vehicle, such as a passenger vehicle or heavy truck, without movement of the rumble strip relative to the roadway.

The following description and the annexed drawings set forth certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features according to aspects of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The annexed drawings, which are not necessarily to scale, show various aspects of the invention.

FIG. 1 is a schematic perspective view showing multiple sets of portable rumble strips of a roadway warning system according to an embodiment of the present invention, in which the portable rumble strips extend across one highway lane in spaced relation to one another.

FIG. 2 is a perspective view of one exemplary form of portable rumble strip according to an embodiment of the present invention.

FIG. 3 is a perspective view of the portable rumble strip in FIG. 2 rolled into a spiral.

FIG. 4 is an enlarged perspective view of an end portion of the rumble strip in FIG. 2 showing an exemplary grip.

FIG. 5 is a lateral cross-sectional view of the rumble strip taken about the line 5-5 in FIG. 4 .

FIG. 6 is a longitudinal cross-sectional view of the rumble strip in FIG. 2 .

FIG. 7 is a lateral cross-sectional view of another exemplary portable rumble strip according to an embodiment, which is shown with exemplary high-density filler being dispensed into an exemplary cavity.

FIG. 8 is a longitudinal cross-sectional view of the portable rumble strip in FIG. 7 .

FIG. 9 is a longitudinal cross-sectional view of another exemplary portable rumble strip according to an embodiment having another exemplary high-density filler.

FIG. 10 is a lateral cross-sectional view of the portable rumble strip in FIG. 9 .

DETAILED DESCRIPTION

The principles and aspects according to the present disclosure have particular application to portable rumble strips for high-speed use, and thus will be described below chiefly in this context. It is understood, however, that the principles and aspects according to the present disclosure also may be applicable to other rumble strips for other applications, such as for low-speed applications.

Referring to FIG. 1 , an exemplary portable roadway warning device 10, or system, is shown deployed on a roadway 12, such as a highway, to provide a perceptible noise and physical warning vibration to an operator of a vehicle 14 when the vehicle drives over the warning system 10. In the illustrated embodiment, the roadway warning system 10 includes a plurality of spaced apart portable rumble strips 16, each of which is deployed to span across at least a portion of a roadway 12. As shown, each rumble strip 16 of the warning system 10 may be an independent portable unit, although the warning system 10 may include rumble strips 16 operably coupled together, such as end-to-end, which may depend on the length of the rumble strip 12 and/or the width of the roadway 12, for example.

FIG. 2 shows an enlarged view of an exemplary portable rumble strip 16 of the warning system 10 is shown. Generally, the portable rumble strip 16 has an elongated body 18, including an upper or top vehicle engagement surface 20 and a lower or bottom roadway engagement surface 22. Connecting the upper surface 20 and lower surface 22 are respective edges, or sides, including a leading edge 24 for receiving initial impact from the vehicle, an opposite trailing edge 26, and lateral side edges 27, 28 that connect the leading and trailing edges 24, 26. The distance between the upper surface 20 and the lower surface 22 generally defines an overall thickness, T, of the rumble strip 16, which may correspond to an overall thickness of the edges 24, 26, 27 and 28. The rumble strip 16 may have a generally uniform thickness T, or the thickness may vary in the longitudinal and/or lateral directions. As shown, the elongated body 18 has a length, L, between the lateral side edges 27, 28 that is greater than a width, W, between the leading and trailing edges 24, 26. In addition, the width W between the upper surface 20 and the lower surface 22 is greater than the thickness T of the rumble strip 16.

Although the dimensions of the rumble strip 16 may vary, the elongated body 18 desirably may be of sufficient length L to reach across a single highway lane, which typically is 11 feet wide, and as such the elongated body 18 may be in a range from 8 feet to 11 feet in length. The rumble strip 16 may have its width W in a range between 8 inches and 16 inches. In addition, the rumble strip 16 should be of sufficient thickness T to generate a noticeable audible and physical vibration to warn the vehicle operator, including truck drivers, when driving over the rumble strip 16, but the thickness T should not be so severe as to startle the drivers, and should not cause damage or adversely affect the stability of the vehicles. To that end, the exemplary rumble strip 16 may have its thickness T in a range between 0.5 inch and 1 inch, and more preferably may be about 0.75 inches, for example.

To facilitate ease of portability and enable the rumble strip 16 to be picked up and transported by hand, the elongated body 18 of the portable rumble strip 16 may include one or grips 30. As shown in the enlarged view of FIG. 3 , for example, the grips 30 may be in the form of hand grip slots. The grips 30 may be adjacent to one or both lateral side edges 27, 28 of the rumble strip body 18, as shown. Although not shown in the illustrated embodiment, one or both of the lateral side edges 27, 28 of the elongated body may include a suitable connector for connecting the rumble strip 16 to another rumble strip of the portable warning system 10. This may be particularly desirable where the roadway is wide, or the overall length L of the rumble strip 16 is less than 8 feet.

In exemplary embodiments, the elongated body 18 of the rumble strip 16 has sufficient flexibility to permit the rumble strip 16 to be rolled up lengthwise from one lateral side edge 27 to the other lateral side edge 28 (end-to-end) for ease of transportation and storage when not in use, and just as easily unrolled during deployment of the rumble strip 16. Such rolling may include simply folding or bending the rumble strip 16 essentially in half so that the lateral side edges 27 and 28 are brought closer together, or may include rolling the rumble strip 16 in a spiral pattern, as shown in FIG. 3 for example. When rolled into a spiral roll, the rumble strip 16 may have an outer diameter between about 18 inches and 48 inches, for example.

To achieve such flexibility, the elongated flexible body 18 of the rumble strip 16 is made with a base material of one or more suitably resilient or flexible materials. Such resilient or flexible materials may include one or more suitable types of polymer, such as suitable elastomeric materials, including by way of non-limiting example: natural rubber, ethylene propylene diene monomer rubber (EPDM), styrene-butadiene rubber (SBR), butyl-rubber, nitrile-rubber, or other thermoset or thermoplastic elastomers, such as polyurethane, including any combinations of the foregoing.

Because the flexible material(s) of the type(s) described above generally have a density of about 0.04 lb/in³ to about 0.05 lb/in³ the flexible material(s) of the rumble strip body 18 on their own do not provide sufficient pressure on the roadway surface to remain in place under heavy traffic at higher end highway speeds. Accordingly, the exemplary portable rumble strip 16 described herein uses high-density filler material within a flexible material matrix of the rumble strip body 18 to achieve a desired overall part density that enables the rumble strip 16 to be suitable for use in high-speed traffic conditions, while also providing enhanced freedom of flexibility in multiple directions to aid in performance and portability of the rumble strip design.

Referring to the lateral cross-sectional view of FIG. 5 and the longitudinal cross-sectional view of FIG. 6 , one exemplary form of the flexible rumble strip body 18 made with a high-density composite 32 having a flexible material matrix 34 and at least one high-density filler material 36 dispersed in the matrix 34 is shown. As described in further detail below, the amount and combined weight of the high-density filler material 36 dispersed in the flexible material matrix 34 should be sufficient to cause the rumble strip 16 to stay in place under heavy traffic at highway speeds, but should not make the rumble strip 16 so heavy that it cannot easily be rolled up or moved by one or two persons. For example, the overall weight of the rumble strip body 18 approximately 11 feet in length by about 1 foot wide by about 0.75 inch thick may be in a range from about 75 lbs. to about 125 lbs., such as about 100 lbs. In addition, the high-density filler material 36 preferably is dispersed within the flexible material matrix 34 in a manner that provides enhanced freedom of flexibility of the rumble strip body 18 in multiple directions to thereby aid in the performance, conformability to the road surface, portability, or storability of the rumble strip.

As shown in the lateral cross-sectional view of FIG. 5 , the high-density composite 32 having the flexible material matrix 34 and high-density filler 36 may constitute essentially the entirety of an upper portion 38 of the flexible rumble strip body 18, including the upper vehicle engagement surface 20, an intermediate (e.g., middle or center) portion 40 between the upper surface 20 and lower surface 22, and a majority of the respective edges 24, 26, 27 and 28. As shown in the longitudinal cross-sectional view of FIG. 6 , the high-density composite 32 forms a portion of the rumble strip body 18 in the longitudinal direction, which may be along a majority of the rumble strip length, or essentially an entirety of the rumble strip length. In exemplary embodiments, one or more additional portions or layers of flexible material may be provided in the rumble strip body 18, such as a lower or bottom portion 42 that includes the lower surface 22. As described in further detail below, the lower portion or layer 42 may be formed with a different flexible material composition than that of the upper portion 38 having the high-density filler 36 (also referred to as the upper composite layer 38 or high-density composite layer 38 in this embodiment).

As shown in the cross-sectional view, the upper vehicle engagement surface 20, the lower roadway engagement surface 22, the trailing edge 26, and the lateral side edges 27 and 28, each may be substantially flat surfaces, with the trailing edge 26 and side edges 27, 28 being perpendicular to the upper and lower surfaces 20, 22. The leading edge 24 of the rumble strip body 18 that faces toward oncoming vehicle traffic may be tapered or beveled to reduce any possible movement of the rumble strip caused by initial contact of the vehicle tires with the rumble strip. The included angle of the tapered or beveled leading edge 24 may be in the range from about 10-degrees to about 15-degrees, for example. The shape and dimensions of any of these surfaces 20, 22, 24, 26 and 28 may be modified as desired to achieve certain functionality of the rumble strip 16. For example, the upper vehicle engagement surface 20 may be cambered or rounded in the width direction between the leading and trailing edges 24, 26. Likewise, the trailing edge 26 could be tapered or beveled similarly to the leading edge 24.

To provide a better grip between the lower surface 22 and the roadway, or to reduce possible skidding of vehicle tires against the upper surface 20, one or both of the upper and lower surfaces 20, 22 of the rumble strip body 18 may have texturing 44. The texturing 44 may be in any suitable form, such as in the form of an open diamond pattern (as best shown in FIG. 4 ) to provide a channel effect to permit the escape of water from both underneath and above the rumble strip 16.

As noted above, the lower portion or layer 42 of the flexible rumble strip body 18 may be formed with a different flexible material composition than that of the upper high-density composite layer 38 having the high-density filler 36. The flexible material composition of the lower layer 42 may be made of any suitable flexible material composition, which may or may not be a composite having additional filler material contained within a flexible material matrix of the lower layer 42.

To further increase the grip between the lower surface 22 of the rumble strip and the roadway, the lower layer 42 of the rumble strip body may be made with a softer polymer material than the flexible matrix material 34 of the upper layer 38. For example, the lower layer 42 of the rumble strip body 18 may have a Shore A hardness in a range from about 40 to about 60, such as about 45; and the upper high-density composite layer 38 may have a Shore A hardness in a range from about 65 to about 80, such as about 75. This may enable the lower layer 42 to better conform to an uneven roadway surface to enhance contact area, while enabling the upper layer 38 to better withstand highspeed vehicle impact. It is understood, however, that these relative hardnesses between layers 38, 42 (or any other layers) may be the same, or may be varied as desired.

Because the upper portion 38 and/or intermediate portion 40 of the rumble strip body 18 may contain the high-density filler 36 while the bottom portion 42 does not, the thickness or volume of the high-density composite 32 (i.e., upper composite layer 38 in the illustrated embodiment) may be several times greater than the thickness or volume of the lower portion 42. For example, where the overall thickness T of the rumble strip body 18 is approximately 0.75 inches, the thickness T1 of the upper portion 38 may be approximately ⅝ inch and the thickness T2 of the lower portion 42 may be approximately ⅛ inch, for example. This can enable the lower portion 42 to provide functional conformance and damping, for example, without providing too much material that is absent the high-density filler 36, which could otherwise affect the overall (average) part density and thus roadway stability.

In exemplary embodiments, the upper high-density composite layer 38 is integrally formed with the flexible material of the lower layer 42 (or other layers, if any), such as via co-vulcanizing of the layers, thereby forming a unitary flexible body 18 of the rumble strip. In such a co-vulcanizing process, the respective flexible materials (e.g., elastomeric polymers) of both the upper layer 38 and lower layer 42 are heated and cured such that the polymeric chains of both layers 38, 42 are crosslinked together to form a unitary structure. The co-vulcanizing process may occur during co-molding of the respective layers under heat and pressure. In the illustrated embodiment, for example, due to crosslinking of the flexible material(s) between layers 38 and 42, including the flexible material(s) of the composite 32, the overall rumble strip body 18 is considered to be a single unitary body.

Although the layers 38 and 42 (and/or other layers, if any) may be integrally formed into a unitary structure as noted above, alternative processing techniques for forming the flexible body 18 also may be employed. For example, alternatively or additionally to co-vulcanizing and/or co-molding, the heated viscous material of one or both layers 38, 42 (or other layers, if any) may impregnate the other layer. Alternatively or additionally, at least one of the layer portions 38 or 42 could be preformed and precured as a discrete article, and the other layer portion(s) 38 or 42 could be formed on the preformed article in which the heated viscous material of the second formed article impregnates the preformed article. Alternatively, the upper and lower portions 38, 42 (or other portions, if any) could be molded as discrete articles and bonded together with a suitable adhesive, such as an adhesive that provides porous wicking and/or crosslinking (after heating/curing) with one or both of the upper and lower portions 38, 42. Although these alternative processing techniques may be employed, it may be preferred that multiple layers of the flexible body 18 (e.g., upper and lower layers 38, 42 including composite 32), if any, are formed as integral and unitary with each other such as by co-vulcanization/crosslinking. This can improve the durability of the rumble strip design by reducing and eliminating interfaces between layers, and also can improve the overall flexibility of the rumble strip design. It is furthermore understood that although the upper and lower portions 38, 42 are shown as distinct layers of different material, the entirety of the rumble strip body 18 could be fabricated with the flexible high-density composite 32 having the high-density filler 36 contained within.

As indicated above, the high-density composite 32 of the rumble strip body includes a flexible material matrix 34 and at least one high-density filler material 36 dispersed in the matrix 34. The high-density composite 32 also may include other materials to aid in the performance of the rumble strip or to aid in the fabrication of the rumble strip, as may desired. For example, the high-density composite 32 may include minor constituent materials used to aid in the processing of the polymeric (e.g., elastomeric) material, such as processing aids, curatives, or other constituent materials. These various ingredients of the exemplary composite composition (also referred to as a “compound”) will be described in further detail below.

Flexible Material Matrix

The flexible material matrix 34 of the high-density composite 32 may include any suitable polymeric material or combination of polymeric materials that provides a desired flexibility of the rumble strip body 18, and also which enables a desired distribution of the high-density filler material 36 within the flexible material matrix 34. By way of non-limiting example, the flexible material of the matrix 34 may include suitable elastomers, including natural rubber, ethylene propylene diene monomer rubber (EPDM), styrene-butadiene rubber (SBR), butyl-rubber, nitrile-rubber, or other thermoset or thermoplastic elastomers, such as polyurethane, or the like, including any combinations of the foregoing. In exemplary embodiments, one or more or all of the polymeric matrix materials are cured (vulcanized) to form a crosslinked polymeric matrix. The density of only the flexible polymer material portion(s) of the rumble strip body 18 (without accounting for the high-density filler 36 or other materials) generally is in the range from 0.035 lb/in³ to 0.050 lb/in³.

Processing Aids, Curatives, and Other Constituent Materials

The high-density composite 32 (e.g., upper composite layer 38) and other polymeric portions of the rumble strip body (e.g., lower layer 42), if any, may include other constituent materials, or remnant traces thereof, including processing aids, curatives, or other minor constituent materials used to aid in the processing of the polymeric (e.g., elastomeric) material. For example, without limitation, during compounding of the high-density composite 32, the polymeric compound of the flexible matrix material 34 may include, in addition to elastomer(s), the following additional ingredients (with exemplary amounts in parts by weight per hundred polymer (e.g., elastomer) where “hundred polymer” (e.g., “hundred elastomer”) as used herein means 100 parts by weight total polymer(s) (e.g., total elastomer(s)): processing oils/aids (from about 0 to about 75 phr), antidegradants (from about 0 to about 10 phr), curatives (from about 0 to 10 phr), accelerators (from about 0 to about 10 phr), coupling agents (from about 0 to about 30 phr), colorants, and the like. These ingredients or other suitable ingredients may be added as noted, increased, decreased, or omitted, as may be desired to achieve the desired propert(ies) of the flexible material matrix 34.

High-Density Filler Material

It has been found that the portable rumble strip body 18 having an overall body density greater than 0.06 lb/in³, and more preferably about 0.08 lbs/in³ or greater, provides acceptable road stability at highway vehicle speeds. As noted above, the density of only the flexible polymer material portion(s) of the rumble strip body 18 (without accounting for the high-density filler 36 or other materials) generally is in the range from 0.035 lb/in³ to 0.050 lb/in³, which falls which below the desired overall rumble strip body density.

Accordingly, the exemplary rumble strip 16 provides the high-density filler material 36 dispersed in the flexible material matrix 34 of the rumble strip body in an amount that achieves an overall part density greater than 0.06 lb/in³, and more preferably at least about 0.08 lb/in³ or greater, such as an overall part density in the range from 0.06 lb/in³ to 0.15 lb/in³. This increased density of the rumble strip body 18 restricts movement of the portable rumble strip by vehicle impact, or raising up from the roadway caused by the trailing draft of passing vehicles. In exemplary embodiments, this increased overall part density is achieved without the use of rigid metal ballast inserts such as solid metal bars molded into the flexible body 18 or attached to the body. As used herein, the term “overall part density” or “overall body density” refers to an overall density of the entire elongated flexible body 18 of the rumble strip 16; whereas the phrase “composite material density” or “layer density” refers to an overall or aggregate density of that particular layer or composite portion of the body 18.

The high-density filler material 36 (also referred to as high-density filler 36) may be any suitable material (or combination of materials) in any suitable form (or combination of forms) that is mechanically mixable, dispersible, and fixable within the flexible material matrix 34 prior to permanently forming the high-density composite 32 of the rumble strip body 18. This is in contrast with conventional rigid metal ballast inserts, like metal bars or other large pieces of metal such as those greater than 10 mm in length (e.g., metal slugs, or the like), which cannot practically be mixed and dispersed within the flexible material matrix 34, but instead are inserted and then molded in place. The distribution of the high-density filler 36 in the flexible material matrix 34 may be achieved by any suitable technique, such as via conventional elastomeric mixing techniques (e.g. internal mixers, mills or extruders) and conventional molding techniques (e.g., compression molding and vulcanizing, transfer and injection molding, or the like).

As indicated above, the high-density filler material 36 is dispersed within the flexible material matrix 34 in a manner that provides enhanced freedom of flexibility of the rumble strip body 18. This enhanced freedom of flexibility may include flexibility in multiple directions of the rumble strip body 18, such as in two or more of the x-(lateral), y-(longitudinal) and z-(vertical) directions (illustrated in FIG. 2 ). For example, the enhanced flexibility of the rumble strip body 18 may include flexibility and resiliency of the upper vehicle engagement surface 20 that absorbs impact from the vehicle. The flexible body 18 should possess acceptable physical durability to withstand the continuous impacting forces from heavy vehicle traffic, including that of semi-trucks for example. In addition, the lower roadway engagement surface 22 may have sufficient flexibility such that it can conform to an uneven roadway surface or crown. The increased contact area provided by such a lower flexible surface 22 enhances the resistance to sliding or movement during impact from moving vehicles. Furthermore, an intermediate portion 40, or middle, of the flexible body 18 also has sufficient flexibility to enable the flexible movement of the upper and lower surfaces 20, 22 of the body. The flexible intermediate portion 40 also may provide a greater degree of flexibility to enable rolling of the portable rumble strip 16 (as shown in FIG. 3 , for example) to aid in the portable deployment, removal, or storage thereof.

In exemplary embodiments, the high-density filler material 36 is uniformly dispersed throughout the flexible material matrix 34 such that the overall composite 32 has uniform properties, including that of hardness, flexibility, strength, and the like. This is in contrast with conventional rigid metal ballast inserts (such as solid metal bars) that are not dispersed within the matrix, but rather are typically inserted or molded in place at localized regions of the body, which thereby results in less flexibility of the body. Generally, the larger the size of the high-density filler material 36, the more difficult it is to mix and uniformly disperse, and thus the less uniform are the properties of the overall composite, which may affect overall flexibility.

The high-density filler 36 may be in any suitable form, such as powder, particulate, fragments, grains, pellets, balls, short fibers, or the like, which may be in any suitable size or shape, such as round, blocky, elongated, acicular, or the like. A typical size of the individual pieces of high-density filler material 36 may be in a range from about 0.1 micrometers (microns) to about 1 micron, for example; however, the size could be in a range from below about 0.1 microns to about 500 microns. Generally, if the size of the high-density filler 36 is too large and heavy, it can affect processability and uniform distribution of the high-density filler 36 in the flexible material matrix 34. In exemplary embodiments, the size of the high-density filler material 36 has a mean size (D50) in a range from about 0.1 microns to about 1,000 microns, and more particularly in a range from about 0.1 microns to about 500 microns, and even more particularly in a range from about 0.1 micron to about 100 microns, for example.

As noted above, the high-density filler material 36 is provided to increase the overall part density of the rumble strip body 18, and thus the high-density filler material 36 has a density that is greater than that of its surrounding flexible material matrix 34. Also noted above, in exemplary embodiments the high-density filler 36 is loaded in an amount that achieves an overall density of the rumble strip body 18 in the range from about 0.06 lb/in³ to about 0.15 lb/in³, or more preferably at least about 0.08 lb/in³. The amount of high-density filler material 36 (in both weight and volume percent) in the composite 32 will vary based on the density (specific gravity) of the high-density filler material 36 (or combination of high-density materials). For example, Table 1 shows four exemplary compositions in accordance with specific embodiments which show an amount by weight of high-density filler material 36, and other ingredients, in parts per hundred (phr) by weight total elastomer(s) of the flexible material matrix 34.

TABLE 1 Parts (phr) Ingredient Ex. 1 Ex. 2 Ex. 3 Ex. 4 Elastomer(s) 100 100 100 100 High-Density Filler Lead Oxide (PbO) 250 Iron Oxide (Fe₃O₄) 900 Zinc Oxide (ZnO) 800 Barium Sulfate (BaSO₄) 1000 Plasticizer Oil 10 10 10 10 Vulcanization/Processing Aids 10 10 10 10 Total Parts 370 1020 920 1120 Density, Pounds per Cubic Inch 0.09 0.13 0.12 0.12

Although only four different types of high-density filler 36 are shown in Examples 1-4 of Table 1, the exemplary composition of the high-density composite 32 is not limited these specific types. Generally, exemplary types of the high-density filler material 36 may include, but is not limited to, oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements. Examples of such metal elements forming the oxides, carbides, sulfates, etc., of the high-density filler include, but are not limited to, calcium, barium, magnesium, iron, zinc, and lead, among others. Some types of these materials will be better suited based on environmental conditions (e.g., corrosion-resistance), processability with the polymeric or elastomeric matrix 34, or cost, among other considerations, as discussed in further detail below.

Generally, the amount and density of the high-density filler material 36 is sufficient to achieve the desired overall part density of the rumble strip body 18, while also enabling suitable volumetric loading of the high-density filler 36 in the flexible material matrix 34 without significantly affecting the flexibility and performance of the rumble strip design. As is evident from the Examples in Table 1, the amount by weight of high-density filler material 36 in the composite will vary based on the density (specific gravity) of the high-density filler material (or combination of materials) because this will affect the volumetric ratio of high-density filler to flexible matrix material 34. Because the elastomer(s) of the flexible material matrix 34 have a density of about 0.04 lb/in³ to about 0.05 lb/in³, and because the desired overall density of the rumble strip body 18 is preferably about 0.08 lb/in³ or greater to achieve the desired weight and road stability for highway vehicle speeds, it has been found that using fillers with a specific gravity below 3.0 makes it difficult to attain the other desired properties (e.g., flexibility, strength, etc.) of the flexible body 18. This is because a filler material with a specific gravity below about 3.0 may require too much to be added to attain a targeted material density of at least 0.08 lb/in³, and as the filler loading increases, the desired properties of the composite (compression set, permanent set, elongation, flexibility, etc.) decrease. Thus, a specific gravity of the high-density filler 36 (or average specific gravity of the combination of materials in the filler 36) may be at least about 3.0 or greater, such as in a range from 3.0 to 20.0, for example.

By way of comparative example, if the 250 parts of lead oxide (PbO) in Example 1 were replaced with talc (magnesium silicate), then this would require 1500 parts to achieve the same 0.09 lb/in³ density, and this amount of talc would not result in a suitable compound. This is because talc has a specific gravity of 2.6 and lead oxide (litharge) has a specific gravity of 9.5. Generally, based on a specific gravity of the high-density filler being at least about 3.0, an exemplary amount of the high-density filler 36 (or combination of high-density fillers) in the composite composition may be in a range from about 100 phr to about 1100 phr (parts by weight per 100 parts by weight of total polymer(s) (e.g., total elastomer(s)) of the flexible polymer matrix 34), such as about any of 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 or 1100 phr, which may be based on the specific gravity of the high-density filler(s) 36.

Because the high-density composite 32 of the rumble strip body 18 may constitute only a portion of the overall rumble strip body 18, the high-density composite portion (i.e., upper composite layer 38 in the illustrated embodiment) may require a density greater than 0.08 lb/in³ to compensate for the relative lower density of the other part(s) of the body (e.g., lower portion 42 in the illustrated embodiment). Accordingly, based on the volume of the high-density composite 32 in the rumble strip body 18 relative to other portions, the high-density composite portion may have a density in a range from 0.08 lb/in³ to 0.15 lb/in³, and more preferably in a range from 0.09 lb/in³ to 0.15 lb/in³, such as about any of 0.09, 0.10, 0.11, 0.12, 0.13, or 0.14 lb/in³, or greater. As noted above, when averaged together, the density of the high-density composite portion(s) and the other portion(s) of the body (e.g., lower portion 42), if any, should have an overall part density greater than 0.06 lb/in³, and more preferably about 0.08 lb/in³ or greater. Based on the overall (averaged) part density, the weight of the rumble strip body having dimensions of 11 ft.×1.0 ft.×0.75 in. may be in a range from 75 to 150 lbs., for example.

In exemplary embodiments, it may be advantageous to use high-density filler material(s) 36 that are resistant to corrosion in a typical roadway condition where road salts such as sodium chloride may be present. This is because, although the high-density filler 36 (e.g., particles) generally will be encapsulated and protected by the flexible material matrix 34, fissures may develop in the matrix 34 over time which can expose the high-density filler 36 to the corrosive elements. Many alkaline earth, transition, or post transition metal oxides, carbides, nitrides, sulfates, and the like, will exhibit corrosion-resistance in a typical roadway condition, and should improve over the corrosion susceptibility of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials.

As discussed above, it is preferable that the specific gravity of the high-density filler material 36 is greater than about 3.0, which may somewhat limit the available candidates of materials that also offer corrosion-resistance. The high-density fillers of PbO, ZnO, Fe₃O₄, and BaSO₄ depicted in Table 1 are some non-limiting examples of oxide and sulfate materials that are corrosion-resistant. The general corrosion resistance of such oxide, carbide, nitride, sulfate, etc. materials are in contrast with some pure metals or metal alloys, such as pure iron, cast iron, or plain carbon steel, for example, which generally form rust in the form of hematite (Fe₂O₃) which is an unstable oxide that spalls off and provides no corrosion-resistant effect. Thus, in exemplary embodiments, the rumble strip body is devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials; and also may be devoid of other pure metals/metal alloys that form an unstable oxide (e.g., those with a Pilling-Bedworth ratio of less than about 1 and greater than about 2).

In addition, some metal oxides, nitrides, carbides, sulfates, inorganics, minerals, etc. (such as some listed in Table 1), may be less expensive, less reactive, less toxic, more processible with the elastomer, etc., than their base metal itself. Therefore, the oxide, nitride, sulfate, etc. form of the high-density filler material 36 may be more desirable from this perspective as well, provided such material is suitable for increasing the density of the composite 32 without detrimental effects to the flexible material matrix 34.

In addition to one or more of the foregoing attributes of providing high density (e.g., specific gravity greater than 3.0), general processability, corrosion-resistance, cost, availability, etc., it may be beneficial to use a high-density filler material 36 that also can be used as a processing aid to the polymer matrix material 34 (e.g., elastomeric). In exemplary embodiments, zinc oxide (ZnO) is a particularly attractive material because it may be used as an accelerator in polymeric (e.g., elastomeric) compositions. In this manner, the ZnO material may be added in a sufficient quantity as an accelerator to the polymer matrix material (e.g., elastomeric) composition, and then can be overloaded to an amount that achieves the desired composite layer 32 density and/or overall part density of the rumble strip body 18. Zinc oxide is a readily-available, inexpensive, non-toxic, and corrosion-resistant material. Zinc oxide also has a specific gravity of about 4.4, meaning that an appropriate amount may be added to the composite composition without affecting the desired properties of flexibility, strength, etc. of the rumble strip body 18. In exemplary embodiments, the ZnO is provided in the high-density composite 32 in an amount from about 500 phr to about 1100 phr (parts by weight per 100 parts by weight of total polymer(s) (e.g., total elastomer(s)) of the flexible polymer matrix 34), and more particularly from about 600 phr to about 800 phr. In exemplary embodiments, the ZnO is added in powder form with a particle size having a range from about 0.1 micron to about 0.5 microns, more particularly 0.1-0.2 microns, to enable suitable performance of the rumble strip design.

While an exemplary form or forms of the portable roadway warning system 10 (and more particularly the exemplary portable rumble strip 16) have been described above, it should be apparent to those having ordinary skill in the art that alternative configurations also could be employed. For example, although the rumble strip body 18 is shown and described with the high-density composite 32 forming at least the upper portion 38, including the vehicle engagement surface 20 and at least a portion of the side surfaces 24, 26, 27 and 28, the high-density composition 32 could instead form one or more intermediate layers or portions (e.g., within intermediate portion 40) between the lower layer 42 and corresponding upper layer (each of which lower and upper layer might not contain high-density filler material as described above, or each of which may have a density less than 0.060 lb/in³). As indicated above, the different layers (e.g., lower, intermediate and upper layer) could each include different base materials, different fillers, and be of different sizes or locations to provide different functionality as may be desired. Although, as noted above, it is preferred that the high-density composite 32, regardless of its location, is of sufficient density and size (based on its density) to provide the desired weight and road stability of the rumble strip body 18, while still preferably enabling the overall flexibility of the rumble strip design.

Turning now to FIGS. 7 and 8 , another exemplary embodiment of a rumble strip 116 for a roadway warning system is shown in lateral cross-section (FIG. 7 ) and longitudinal cross-section (FIG. 8 ). The rumble strip 116 is similar to the above-described rumble strip 16, and consequently the same reference numerals but indexed by 100 are used to denote structures corresponding to similar structures in the rumble strips 16, 116. In addition, the foregoing description of the rumble strip 16 is equally applicable to the rumble strip 116, except as noted below. Moreover, aspects of the rumble strips 16, 116 may be substituted for one another or used in conjunction with one another where applicable.

As shown, the rumble strip 116 includes an elongated body 118 having an upper vehicle engagement surface 120, a lower roadway engagement surface 122, and a leading edge 124 and trailing edge 126 between the upper and lower engagement surfaces 120, 122. Similarly to the rumble strip 16, in exemplary embodiments the elongated body 118 of the rumble strip 116 has a length greater than its width, and its width greater than its thickness. Also in exemplary embodiments, the rumble strip body 118 may be a flexible body 118 to provide enhanced freedom of flexibility in multiple directions to aid in performance and portability of the rumble strip design, among other considerations. To achieve such flexibility, one or more portions of the rumble strip body 118 may be made with one or more suitably resilient or flexible materials, including processing aids and other constituents, such as those materials described above.

At least one difference between the exemplary rumble strip 116 and the above-described rumble strip 16 is that the high-density filler material 136 of rumble strip 116 is in the form of discrete unbound pieces of material disposed within a cavity 137 of the body 118, instead of being discrete pieces dispersed and embedded in a polymer matrix as is the case with exemplary embodiments of the rumble strip 16. Such a design with the discrete unbound pieces of high-density filler material 136 may enable a greater variety in the type of material that can be included in the rumble strip body 118 because dispersing the material within a matrix is not a concern. Moreover, because the discrete unbound pieces of the filler material 136 may be movable against each other and/or displaceable relative to each other within the cavity 137, this may enable the rumble strip body 118 to maintain at least some flexibility by permitting deformations (flexion, compression, etc.) within the overall bulk of discrete unbound pieces in the cavity 137. In addition, because the overall bulk of high-density filler material 136 is in the form of individual and preferably small pieces, each individual piece preferably would not have sufficient mass to create an impactful projectile if ejected from the rumble strip 116 in the event of catastrophic failure. Rather, the discrete unbound pieces of high-density filler 136 would be dispersed from the cavity 137 as a cloud, for example.

The discrete unbound pieces of high-density filler material 136 may include one or more types of material in any suitable form or forms. In exemplary embodiments, the discrete unbound pieces provide a bulk flowable material that partially or entirely fills the cavity 137 of the body 118. The flowable material may be poured into the cavity 137 and may remain relatively loose to enhance deformability of the body 118, or may be tamped or compacted as it fills the cavity 137, or thereafter, to increase packing density. The flowable material may be a free-flowing material with a high-degree of flowability, or the flowable particulate may have a lower-degree of flowability with some cohesion between particles. Generally, a bulk flowable material enables at least some displacement of its constituent solid pieces relative to each other. The degree of flowability will be influenced by a variety of factors, such as friction between particles, Van der Waals or static forces, storage environment, moisture, etc. A suitable test method, such as with the use of a powder rheometer, may be used to determine the flowability. Generally, the higher degree of flowability of the material will enhance pourability into the cavity 137 and also may enhance flexibility of the rumble strip body 118 due to the easier movement of the particles against each other.

In exemplary embodiments, the discrete unbound pieces of high-density filler 136 include one or more types of particles which may be in powder form. The particles may have any suitable shape and size (or size distribution) as may be desired for the physical properties of the bulk material. The particles may be generally spherical or have a low aspect ratio, or may be irregular or have a high aspect ratio. Irregular particles generally will have greater resistance to flow but may provide improved compaction (green strength) if desired. The particle size for such powders may be in a range from about 0.1 microns to about 500 microns, for example. Finer particles generally have greater surface area and may have a higher resistance to flow. Larger pieces greater than 500 microns also could be used, such as pieces as large as about 1 millimeter (mm), or possibly greater. The greater the mass of each individual piece, however, the greater the impact force of the piece if ejected from the cavity 137 of the rumble strip body 118 (i.e., in the event of catastrophic failure). Therefore, pieces smaller than 1 mm, and more particularly a flowable powder having a mean size (D50) from about 100 microns to about 1,000 microns (1 mm) may be preferred. The discrete unbound pieces of high-density filler 136 also may include short-fibers, if desired, or may include aggregate particles composed of many small pieces adhered together. Such an aggregate particle still constitutes a discrete unbound piece that can be intermixed with and movable relative to other discrete unbound pieces of the high-density filler 136 in the cavity 137.

The composition of the discrete unbound pieces of high-density filler 136 may include a single type of material or may include a mixture of different types of material. Generally, exemplary types of material used in the high-density filler 136 may be the same as the high-density filler 36 described above, including but not limited to, one or more of oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements. In the rumble strip 116, however, because the high-density filler 136 is not dispersed within a matrix, there may be less concern over material interactions with the matrix material. In addition, depending on the encapsulation of the overall bulk of high-density filler 136 within the cavity 137, there also may be less concern over environmental corrosion caused by road salts, for example. Accordingly, materials such as pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials may be utilized in the rumble strip 116 with reduced adverse effect. Thus, by way of example and not limitation, an inexpensive flowable iron powder could be dispensed as the high-density filler material 136 into the cavity 137, or other pocket, in the rumble strip body 118.

To facilitate the flowability of the high-density filler 136, the composition of the high-density filler 136 may include materials other than high-density materials. For example, suitable lubricants, such as graphite, stearates (e.g., magnesium stearate), stearic acid, oils, or the like could be used in the composition. The lubricants may be chosen as desired based on their performance and compatibility with the high-density materials in the filler 136. Alternatively or additionally, other suitable materials may be added to the composition of the high-density filler to aid in compaction or packing density, if desired.

Similarly to the above-described rumble strip 16, the amount and type of material(s) in the composition of the high-density filler 136 should be chosen to provide an overall density of the rumble strip body 118 that results in sufficient pressure on the roadway surface for acceptable resistance to movement, such as for use in high-speed traffic conditions. Accordingly, in exemplary embodiments the high-density filler 136 is loaded into the cavity 137 in an amount that achieves an overall density of the rumble strip body 118 in the range from about 0.06 lb/in³ to about 0.15 lb/in³, or more preferably at least about 0.08 lb/in³. The amount of high-density filler 136 (in both weight and volume percent) in the cavity 137 will vary based on the density (specific gravity) of the high-density filler material 136 (or combination of materials in the high-density filler 136). Similarly to the rumble strip 16, the body 118 of the rumble strip 116 may be made with polymer(s) (e.g., elastomer(s)) having a density of about 0.04 lb/in³ to about 0.05 lb/in³; and because the desired overall density of the rumble strip body 118 preferably may be about 0.08 lb/in³ or greater to achieve the desired weight and road stability for highway vehicle speeds, using a high-density filler material 136 (e.g., individually or as a mixture) with a specific gravity below 3.0 may make it difficult to attain the desired overall density of the body 118. Thus, a specific gravity of the high-density filler 136 (e.g., the specific gravity of the material or mixture of materials) may be at least about 3.0 or greater, such as in a range from 3.0 to 20.0, for example. Because some void space may be contained in the cavity 137 such as between individual pieces and/or in a head space of the cavity 137, the calculation of void space may need to be accounted for in determining the desired specific gravity of the high-density filler 136.

The cavity 137 in the rumble strip body 118 may be formed in any suitable manner with any suitable configuration as may be desired for the application. In the illustrated embodiment, the cavity 137 is a hollow chamber formed by internal surfaces 141 of the body 118. For example, the rumble strip body 118 may be molded as a hollow article, and a fill port 150 may be provided at any suitable location to allow the discrete unbound pieces of high-density filler material 136 to be dispensed into the cavity 137 via the fill port 150. A suitable closure 152, such as a plug, is provided to close and seal the cavity 137 after a desired amount of the high-density filler 136 is dispensed into the cavity 137. The amount of high-density filler 136 may at least partially fill the cavity 137, or may entirely fill the cavity 137 with suitable void space to permit flowability of the filler 136 in the cavity thereby enhancing flexibility of the body 118.

The cavity 137 may be located at any suitable position in the body 118 to account for weight distribution, flexibility, etc. In the illustrated embodiment shown in FIG. 7 , for example, the cavity 137 is essentially centrally located in the lateral direction of the body 118 and extends laterally along a majority of the width of the body 118. As shown in FIG. 8 , the cavity 137 may extend in the longitudinal direction along at least a portion of the length of the rumble strip body 118. To facilitate fillability, multiple cavities 137 may be provided in the body 118, such as a plurality of longitudinally spaced apart cavities 137 each having a fill port 150 and at least partially filled with high-density filler 136, which may be the same type of filler, or different types as desired.

In an alternative embodiment (not shown), the discrete unbound pieces of high-density filler 136 may be dispensed into a bag or bladder that is then co-molded with the rumble strip body 118 to form the cavity 137 filled with the high-density filler 136. Any suitable bag or bladder capable of withstanding the processing conditions of molding the body 118 may be used. The bag or bladder filled with high-density filler 136 may be introduced at any step during the molding process and may be positioned at any suitable location. Multiple bags or bladders filled with high-density filler 136 may be used and positioned in the body 118. In exemplary embodiments, the bag or bladder may be made with a compatible polymer (e.g., elastomer) that provides flexibility and which may enable co-vulcanization with the surrounding portions of the rumble strip body 118.

Similarly to the rumble strip 16, the body 118 of rumble strip 116 may be made of the same material (e.g., flexible polymeric, such as one or more elastomers), or may be made of different materials. For example, similarly to rumble strip 16, the lower portion 142 of the rumble strip body 118 may be made with a softer polymer material the upper portion 139. This may enable the lower portion 142 to better conform to an uneven roadway surface to enhance contact area, while enabling the upper portion 139 to better withstand highspeed vehicle impact. It is understood, however, that these relative hardnesses between portions 139, 142 (or any other portions or layers) may be the same, or may be varied as desired. In exemplary embodiments, the upper portion 139 is integrally molded with the lower portion 142 (or one or more other layers, if any), such as via co-vulcanizing. The co-vulcanizing process may occur during co-molding of the respective layers under heat and pressure. Alternatively or additionally, the heated viscous material of one or both layers 138, 142 (or other layers, if any) may impregnate the other layer. Alternatively or additionally, at least one of the layer portions 138 or 142 could be preformed and precured as a discrete article, and the other layer portion(s) 138 or 142 could be formed on the preformed article in which the heated viscous material of the second formed article impregnates the preformed article. Alternatively, the upper and lower portions 138, 142 (or other portions, if any) could be molded as discrete articles and bonded together with a suitable adhesive, such as an adhesive that provides porous wicking and/or crosslinking (after heating/curing) with one or both of the upper and lower portions 138, 142. Alternatively, the upper and lower portions 138, 132 may form respective portions of an openable and closeable rumble strip body in the form of a container or case containing the discrete unbound pieces of high-density filler 136.

Turning now to FIGS. 9 and 10 , another exemplary embodiment of a rumble strip 216 for a roadway warning system is shown in lateral cross-section (FIG. 10 ) and longitudinal cross-section (FIG. 9 ). The rumble strip 216 is similar to the above-described rumble strips 16, 116 and consequently the same reference numerals but in the 200-series are used to denote structures corresponding to similar structures in the rumble strips 16, 116, 216. In addition, the foregoing description of the rumble strips 16, 116 are equally applicable to the rumble strip 216, except as noted below. Moreover, aspects of the rumble strips 16, 116, 216 may be substituted for one another or used in conjunction with one another where applicable.

As shown, the rumble strip 216 includes an elongated body 218 having an upper vehicle engagement surface 220, a lower roadway engagement surface 222, and a leading edge 224 and trailing edge 226 between the upper and lower engagement surfaces 220, 222. Similarly to the rumble strip 16, in exemplary embodiments the elongated body 218 of the rumble strip 216 has a length greater than its width, and its width greater than its thickness. Also in exemplary embodiments, the rumble strip body 218 may be a flexible body 218. To achieve flexibility, one or more portions of the rumble strip body 218 may be made with one or more suitably resilient or flexible materials, including processing aids and other constituents, such as those materials described above.

At least one difference with the exemplary rumble strip 216 is that the high-density filler material 236 is in the form of one or more frangible articles 236 disposed within the rumble strip body 218. In exemplary embodiments, the frangible article(s) 236 are brittle and easily breakable (e.g., can be broken by hand, such as with about 25 pounds of force). As shown in the illustrated embodiment, the one or more frangible articles 236 may be fixed within the rumble strip body 218, such as being encased by the one or more materials forming the rumble strip body 218. Such a design with the frangible article(s) 236 may enable a greater variety in the type of material that can be included in the rumble strip body 218 because dispersing the material within a matrix is not a concern. In addition, because the frangible article(s) 236 are brittle and easily breakable, if a piece of frangible article 236 were ejected from the rumble strip body 218 in event of catastrophic failure, the piece of frangible article would break and/or disintegrate on impact.

The frangible article(s) 236 may include one or more types of material in any suitable form or forms. The material or mixture of materials forming the frangible article 236 may be the same as those described above in connection with the high-density filler 36 and the high-density filler 136. The material or mixture of materials constituting the frangible article 236 may be formed into any suitable structure as desired. For example, the material(s) constituting the frangible article 236 may be pressed into a green state to form the final frangible article 236. Alternatively or additionally, a binder, such as a heat-sensitive binder, may be utilized to facilitate particle-to-particle bonding to form the frangible article 236. The binder may be a weak binder or may be provided in minute amounts to facilitate fragility. The frangible article 236 may have a relatively high-porosity to facilitate fragility. The final shape of the frangible article 236 may be a bar, rod, slug, puck, brick, or any other suitable shape, which may be placed at any suitable location in the rumble strip body 218.

Similarly to the above-described rumble strips 16 and 116, the amount and type of material(s) in the composition of the frangible article 236 should be chosen to provide an overall density of the rumble strip body 218 that results in sufficient pressure on the roadway surface for acceptable resistance to movement, such as for use in high-speed traffic conditions. Accordingly, in exemplary embodiments the frangible article 236 is disposed in the rumble strip body 218 in an amount that achieves an overall density of the rumble strip body 118 in the range from about 0.06 lb/in³ to about 0.15 lb/in³, or more preferably at least about 0.08 lb/in³. Also similarly to the rumble strips 16 and 116, the body 218 of the rumble strip 216 may be made with polymer(s) (e.g., elastomer(s)) having a density of about 0.04 lb/in³ to about 0.05 lb/in³, and to achieve a suitable overall density of the rumble strip body 218, the specific gravity of the frangible article 236 as a whole (e.g., the average specific gravity of the material or mixture of materials forming the frangible article 236) may be at least about 3.0 or greater, such as in a range from 3.0 to 20.0, for example. Because the frangible article 236 may have porosity, the calculation of porosity may need to be accounted for in determining the desired specific gravity or density of the overall frangible article 236.

Also similarly to the rumble strips 16 and 116, the body 218 of rumble strip 216 may be made of the same material (e.g., flexible polymeric, such as one or more elastomers), or may be made of different materials. For example, the lower portion 242 of the rumble strip body 218 may be made with a softer polymer material than the upper portion 239, or vice versa. In addition, the upper portion 239 may be integrally molded with the lower portion 242 (or one or more other layers, if any), such as via co-vulcanizing. The co-vulcanizing process may occur during co-molding of the respective layers under heat and pressure. Alternatively or additionally, the heated viscous material of one or both layers 238, 242 (or other layers, if any) may impregnate the other layer. Alternatively or additionally, at least one of the layer portions 238 or 242 could be preformed and precured as a discrete article, and the other layer portion(s) 238 or 242 could be formed on the preformed article in which the heated viscous material of the second formed article impregnates the preformed article. Alternatively, the upper and lower portions 238, 242 (or other portions, if any) could be molded as discrete articles and bonded together with a suitable adhesive. Alternatively, the upper and lower portions 238, 232 may form respective portions of an openable and closeable rumble strip body in the form of a case containing the frangible article(s) 236.

An exemplary roadway warning device has been described herein, including a portable rumble strip that includes high-density filler material to achieve a desired overall density and roadway stability of the rumble strip such as for use in high-speed traffic conditions without the use of conventional rigid metal ballast inserts. In some exemplary embodiments, the filler is dispersed and embedded within a flexible polymer composite matrix of the rumble strip body. In some exemplary embodiments, the filler is in the form of discrete unbound pieces of material disposed within a cavity of the rumble strip body. In some exemplary embodiments, the filler is in the form of a frangible article disposed within the rumble strip body.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having a flexible polymeric material matrix and at least one filler dispersed in the matrix that enhances the density of the composite, wherein the at least one filler is included in an amount that provides an overall density of the elongated flexible body in a range from 0.06 lb/in³ to 0.15 lb/in³.

According to an aspect, a portable rumble strip includes an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having: a flexible elastomeric matrix, at least one filler dispersed in the matrix, wherein: the at least one filler has a density greater than a density of the flexible elastomeric material matrix; the at least one filler has a specific gravity of 3.0 or greater; and the at least one filler is included in the composite in an amount that enhances the density of the composite, such that an overall density of the elongated flexible body is in a range from 0.06 lb/in³ to 0.15 lb/in³.

According to an aspect, a portable rumble strip includes an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, wherein the portable rumble strip includes a composite having a polymeric material matrix and a filler dispersed in the matrix in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix, wherein the density of the filler is greater than a density of the polymeric material matrix.

Embodiment(s) may include one or more features of the foregoing aspect(s), separately or in any suitable combination, which may be combined with one or more of the following additional features, which may be included separately or in any suitable combination.

In some embodiments, the flexible polymeric material matrix of the composite is co-vulcanized with the one or more additional portions of the body to form a unitary structure.

In some embodiments, the at least one filler is dispersed uniformly throughout the matrix of the composite such that the elongated flexible body is free to flex in multiple different directions at any location along the length of the body that corresponds with the composite.

In some embodiments, the at least one filler has a density greater than a density of the flexible polymeric material matrix.

In some embodiments, the at least one filler has a specific gravity of 3.0 or greater.

In some embodiments, the at least one filler is included in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the flexible polymeric material matrix of the composite.

In some embodiments, the flexible polymeric material matrix has a density of less than 0.060 lb/in³.

In some embodiments, the flexible polymeric material matrix includes a thermoset or thermoplastic elastomer.

In some embodiments, the at least one filler has greater corrosion resistance to sodium chloride than plain carbon steel.

In some embodiments, the at least one filler is in powder form, and an average particle size of the powder is in a range from 0.1 microns to 500 microns.

In some embodiments, the at least one filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element.

In some embodiments, the at least one filler includes one or more of lead oxide (PbO), iron oxide (Fe₃O₄), zinc oxide (ZnO), or barium sulfate (BaSO₄).

In some embodiments, the at least one filler that enhances the density of the composite is ZnO in an amount from 500 parts to 1100 parts by weight per 100 parts by weight total polymer of the flexible polymeric material matrix of the composite.

In some embodiments, the composite, the at least one filler, and/or the flexible polymeric material matrix includes one or more additional materials.

In some embodiments, the composite forms at least one flexible layer that cooperates with one or more additional flexible layers comprising polymeric material such that the elongated flexible body of the rumble strip is free to flex in multiple directions, bend in a direction of the length to bring longitudinal ends of the body toward each other, or roll into a spiral in a direction of the length.

In some embodiments, the density of the composite layer is greater than a density of the one or more additional flexible layers, and an overall average density of all layers of the elongated flexible body in a range from 0.06 lb/in³ to 0.15 lb/in³.

In some embodiments, the composite forms an upper layer including at least the upper vehicle engagement surface, and wherein the one or more additional flexible layers includes a lower layer including at least the lower roadway engagement surface.

In some embodiments, the lower layer is co-vulcanized and unitary with the upper layer to form a single unitary elongated flexible body that is portable as a single unit.

In some embodiments, the upper layer formed by the composite is harder than the lower layer.

In some embodiments, an entirety of the elongated flexible body bounded by its outer surfaces is formed by the composite having the flexible polymeric material matrix and the at least one filler dispersed in the matrix that enhances the density of the composite.

In some embodiments, the composite and/or the elongated flexible body is devoid pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials.

In some embodiments, the rumble strip is devoid of rigid metal inserts, such as those having a minimum size of greater than 10 mm.

In some embodiments, the rumble strip is devoid of a housing that contains the elongated flexible body and/or the composite, and more particularly a housing that is more rigid than that of the composite.

In some embodiments, the overall density of the elongated flexible body in a range of: from 0.07 lb/in³ to 0.15 lb/in³, from 0.08 lb/in³ to 0.15 lb/in³, from 0.09 lb/in³ to 0.15 lb/in³, from 0.10 lb/in³ to 0.15 lb/in³, from 0.11 lb/in³ to 0.15 lb/in³, from 0.12 lb/in³ to 0.15 lb/in³, from 0.13 lb/in³ to 0.15 lb/in³, from 0.08 lb/in³ to 0.14 lb/in³, from 0.09 lb/in³ to 0.14 lb/in³, or any range or subrange below the stated values.

In some embodiments, the elongated flexible body has sufficient strength and flexibility to withstand direct impact from a vehicle weighing at least 3,000 pounds at 50 mph or greater, and more particularly at least about 80,000 lbs. at speeds greater than 80 mph, without failure.

In some embodiments, the elongated flexible body has sufficient strength and flexibility to withstand direct impact from a vehicle weighing at least 3,000 pounds at 50 mph or greater, and more particularly at least about 80,000 lbs. at speeds greater than 80 mph, without significant movement relative to pavement upon which the rumble strip rests, such as less than 1 inch of movement per impact.

In some embodiments, the composite is devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based filler material, and more particularly wherein the elongated flexible body is devoid of such filler materials.

In some embodiments, the at least one filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein the elongated body includes at least one cavity, and at least one filler in the form of discrete unbound pieces of material is disposed within the cavity.

Embodiment(s) may include one or more features of the foregoing aspect, separately or in any suitable combination, which may be combined with one or more of the following additional features, which may be included separately or in any suitable combination.

In some embodiments, the elongated body is a flexible polymeric body or contains flexible portions of the elongated body.

In some embodiments, the at least one filler enhances the density of the composite, and wherein the at least one filler is included in an amount that provides an overall density of the elongated body in a range from 0.06 lb/in³ to 0.15 lb/in³.

In some embodiments, the discrete unbound pieces provide a bulk flowable material in the cavity.

In some embodiments, the discrete unbound pieces provide a free-flowing powder.

In some embodiments, the discrete unbound pieces have a mean size (D50) less than about 1 mm.

In some embodiments, the discrete unbound pieces is a flowable powder having a mean size (D50) from about 100 microns to about 1,000 microns (1 mm).

In some embodiments, the discrete unbound pieces include oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements.

In some embodiments, the cavity is a hollow chamber formed by internal surfaces of the elongated body.

In some embodiments, elongated body includes a fill port in fluid communication with cavity, and optionally a closure to close and seal the cavity.

In some embodiments, the discrete unbound pieces of filler are contained in a bag or bladder that co-molded with the elongated body to form the cavity.

In some embodiments, the bag or bladder is made with a polymer that provides flexibility and is co-vulcanized with surrounding portions of the elongated body.

In some embodiments, the elongated body includes multiple cavities containing the at least one filler, the multiple cavities being spaced apart from each other in the elongated body.

In some embodiments, one or more layers or portions of the elongated body have different properties, the one or more layers or portions being co-vulcanized together to form a unitary portion or entirety of the body.

According to an aspect, a portable rumble strip includes an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein one or more frangible articles are disposed in the elongated body.

Embodiment(s) may include one or more features of the foregoing aspect, separately or in any suitable combination, which may be combined with one or more of the following additional features, which may be included separately or in any suitable combination.

In some embodiments, the elongated body is a flexible polymeric body or contains flexible portions of the elongated body.

In some embodiments, the one or more frangible articles enhance the density of the composite, and wherein the one or more frangible articles are included in an amount that provides an overall density of the elongated body in a range from 0.06 lb/in³ to 0.15 lb/in³.

In some embodiments, the one or more frangible articles are fixed within the elongated body.

In some embodiments, the one or more frangible articles include a bar, rod, slug, puck, brick, or any other suitable shape.

In some embodiments, the one or more frangible articles include oxides, carbides, nitrides, sulfides, sulfates, silicates, inorganics, minerals, metal alloys or pure metals comprising alkaline earth, transition, or post transition metal elements.

In some embodiments, one or more layers or portions of the elongated body have different properties, the one or more layers or portions being co-vulcanized together to form a unitary portion or entirety of the body.

According to an aspect, a portable rumble strip for placement on a roadway in a roadway warning system includes filler material within a body of the rumble strip, the filler material being of a type and in an amount that increases the density of a rumble strip such that its mass can exert a pressure on the roadway to withstand impact from a vehicle, such as a passenger vehicle or heavy truck, without movement of the rumble strip relative to the roadway.

Embodiment(s) may include the foregoing aspect in combination with one or more features of the foregoing aspect(s) or embodiment(s) separately or in any suitable combination.

As used herein, the term “flexible” is used in its conventional meaning to those having ordinary skill in the art, especially to those with ordinary skill in the art of polymeric and elastomeric compounding. Flexibility testing may be achieved by a test method designed to test the resistance to crack growth of a solid polymer, such as an elastomer (e.g., rubber), after repeated flexing. A suitable test method is ASTM D813 (Crack Growth), which is usually measured in the mm growth of a crack, with a lower growth number indicating a better resistance to cracking and increased flexibility. Another suitable test method is ASTM D1052 (Cut Growth Flexing), which gives an estimate of the ability of rubber vulcanizates to resist crack growth of a pierced specimen when subjected to bend flexing. Yet another suitable test is ASTM D2632 which covers the determination of impact resilience of solid rubber from measurement of the vertical rebound of a dropped mass. Still another suitable test may be ASTM 1053 (Stiffness/Flexibility).

As used herein, an “operable connection,” or a connection by which entities are “operably connected,” is one in which the entities are connected in such a way that the entities may perform as intended. An operable connection may be a direct connection or an indirect connection in which an intermediate entity or entities cooperate or otherwise are part of the connection or are in between the operably connected entities. An operable connection or coupling may include the entities being integral and unitary with each other.

It is to be understood that terms such as “top,” “bottom,” “upper,” “lower,” “left,” “right,” “front,” “rear,” “forward,” “rearward,” and the like as used herein may refer to an arbitrary frame of reference, rather than to the ordinary gravitational frame of reference.

It is to be understood that all ranges and ratio limits disclosed in the specification and claims may be combined in any manner. It is to be understood that unless specifically stated otherwise, references to “a,” “an,” and/or “the” may include one or more than one, and that reference to an item in the singular may also include the item in the plural.

The term “about” as used herein refers to any value which lies within the range defined by a variation of up to ±10% of the stated value, for example, ±10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.01%, or ±0.0% of the stated value, as well as values intervening such stated values.

The phrase “and/or” should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

The word “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” may refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “one of,” “only one of,” or “exactly one of.”

The transitional words or phrases, such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “incorporating,” “made of/with,” “formed of/with,” “fabricated of/with,” and the like, are to be understood to be open-ended, i.e., to mean including but not limited to.

Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application. 

1. A portable rumble strip comprising an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having a flexible polymeric material matrix and at least one filler dispersed in the matrix that enhances the density of the composite, wherein the at least one filler is included in an amount that provides an overall density of the elongated flexible body in a range from 0.06 lb/in³ to 0.15 lb/in³.
 2. The portable rumble strip according to claim 1, wherein the flexible polymeric material matrix of the composite is co-vulcanized with the one or more additional portions of the body to form a unitary structure.
 3. The portable rumble strip according to claim 1, wherein the at least one filler is dispersed uniformly throughout the matrix of the composite such that the elongated flexible body is free to flex in multiple different directions at any location along the length of the body that corresponds with the composite.
 4. The portable rumble strip according to claim 1, wherein the at least one filler has a density greater than a density of the flexible polymeric material matrix.
 5. The portable rumble strip according to claim 1, wherein the at least one filler has a specific gravity of 3.0 or greater.
 6. The portable rumble strip according to claim 5, wherein the at least one filler is included in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the flexible polymeric material matrix of the composite.
 7. The portable rumble strip according to claim 5, wherein the flexible polymeric material matrix has a density of less than 0.060 lb/in³.
 8. The portable rumble strip according to claim 7, wherein the flexible polymeric material matrix includes a thermoset or thermoplastic elastomer.
 9. The portable rumble strip according to claim 1, wherein the at least one filler has greater corrosion resistance to sodium chloride than plain carbon steel.
 10. The portable rumble strip according to claim 1, wherein the at least one filler is in powder form, and an average particle size of the powder is in a range from 0.1 microns to 500 microns.
 11. The portable rumble strip according to claim 1, wherein the at least one filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element.
 12. The portable rumble strip according to claim 1, wherein the at least one filler includes one or more of lead oxide (PbO), iron oxide (Fe3O4), zinc oxide (ZnO), or barium sulfate (BaSO4).
 13. The portable rumble strip according to claim 1, wherein the at least one filler that enhances the density of the composite is ZnO in an amount from 500 parts to 1100 parts by weight per 100 parts by weight total polymer of the flexible polymeric material matrix of the composite.
 14. The portable rumble strip according to claim 1, wherein the composite, the at least one filler, and/or the flexible polymeric material matrix includes one or more additional materials.
 15. The portable rumble strip according to claim 1, wherein the composite forms at least one flexible layer that cooperates with one or more additional flexible layers comprising polymeric material such that the elongated flexible body of the rumble strip is free to flex in multiple directions, bend in a direction of the length to bring longitudinal ends of the body toward each other, or roll into a spiral in a direction of the length.
 16. The portable rumble strip according to claim 15, wherein the density of the composite layer is greater than a density of the one or more additional flexible layers, and an overall average density of all layers of the elongated flexible body in a range from 0.06 lb/in³ to 0.15 lb/in³.
 17. The portable rumble strip according to claim 15, wherein the composite forms an upper layer including at least the upper vehicle engagement surface, and wherein the one or more additional flexible layers includes a lower layer including at least the lower roadway engagement surface.
 18. The portable rumble strip according to claim 17, wherein the lower layer is co-vulcanized and unitary with the upper layer to form a single unitary elongated flexible body that is portable as a single unit.
 19. The portable rumble strip according to claim 17, wherein the upper layer formed by the composite is harder than the lower layer.
 20. The portable rumble strip according to claim 1, wherein an entirety of the elongated flexible body bounded by its outer surfaces is formed by the composite having the flexible polymeric material matrix and the at least one filler dispersed in the matrix that enhances the density of the composite.
 21. The portable rumble strip according to claim 1, wherein the composite and/or the elongated flexible body is devoid pure iron, cast iron, plain carbon steel, or other non-stainless iron-based materials.
 22. The portable rumble strip according to claim 1, wherein the rumble strip is devoid of rigid metal inserts, such as those having a minimum size of greater than 10 mm, and/or wherein the rumble strip is devoid of a housing that contains the elongated flexible body and/or the composite, and more particularly a housing that is more rigid than that of the composite.
 23. The portable rumble strip according to claim 1, wherein the overall density of the elongated flexible body in a range of: from 0.07 lb/in³ to 0.15 lb/in³, from 0.08 lb/in³ to 0.15 lb/in³, from 0.09 lb/in³ to 0.15 lb/in³, from 0.10 lb/in³ to 0.15 lb/in³, from 0.11 lb/in³ to 0.15 lb/in³, from 0.12 lb/in³ to 0.15 lb/in³, from 0.13 lb/in³ to 0.15 lb/in³, from 0.08 lb/in³ to 0.14 lb/in³, from 0.09 lb/in³ to 0.14 lb/in³, or any range or subrange below the stated values.
 24. The portable rumble strip according to claim 1, wherein the elongated flexible body has sufficient strength and flexibility to withstand direct impact from a vehicle weighing at least 3,000 pounds at 50 mph or greater, and more particularly at least about 80,000 lbs. at speeds greater than 80 mph, without failure.
 25. The portable rumble strip according to claim 1, wherein the elongated flexible body has sufficient strength and flexibility to withstand direct impact from a vehicle weighing at least 3,000 pounds at 50 mph or greater, and more particularly at least about 80,000 lbs. at speeds greater than 80 mph, without significant movement relative to pavement upon which the rumble strip rests, such as less than 1 inch of movement per impact.
 26. A portable rumble strip comprising an elongated flexible body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated flexible body having a length greater than width and the width greater than thickness, wherein the elongated flexible body incorporates a composite having: a flexible elastomeric matrix, at least one filler dispersed in the matrix, wherein: the at least one filler has a density greater than a density of the flexible elastomeric material matrix; the at least one filler has a specific gravity of 3.0 or greater; and the at least one filler is included in the composite in an amount that enhances the density of the composite, such that an overall density of the elongated flexible body is in a range from 0.06 lb/in³ to 0.15 lb/in³.
 27. The portable rumble strip according to claim 26, wherein the composite is devoid of pure iron, cast iron, plain carbon steel, or other non-stainless iron-based filler material, and more particularly wherein the elongated flexible body is devoid of such filler materials.
 28. The portable rumble strip according to claim 26, wherein the at least one filler is an oxide, carbide, nitride, sulfide, sulfate, silicate, inorganic, or mineral comprising at least one alkaline earth, transition, or post transition metal element.
 29. (canceled)
 30. A portable rumble strip comprising an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, wherein the portable rumble strip includes a composite having a polymeric material matrix and a filler dispersed in the matrix in an amount from 100 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix, wherein the density of the filler is greater than a density of the polymeric material matrix.
 31. The portable rumble strip according to claim 30, wherein the filler includes zinc oxide (ZnO) in an amount between 500 parts to 1100 parts by weight per 100 parts by weight total polymer of the polymeric material matrix of the composite.
 32. (canceled)
 33. A portable rumble strip comprising an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein the elongated body includes at least one cavity, and at least one filler in the form of discrete unbound pieces of material is disposed within the cavity. 34-46. (canceled)
 47. A portable rumble strip comprising an elongated body having an upper vehicle engagement surface, a lower roadway engagement surface, and a leading edge and trailing edge between the upper and lower engagement surfaces, the elongated body having a length greater than width and the width greater than thickness, wherein one or more frangible articles are disposed in the elongated body. 48-54. (canceled)
 55. A portable rumble strip for placement on a roadway in a roadway warning system, the rumble strip comprising filler material within a body of the rumble strip, the filler material being of a type and in an amount that increases the density of a rumble strip such that its mass can exert a pressure on the roadway to withstand impact from a vehicle, such as a passenger vehicle or heavy truck, without movement of the rumble strip relative to the roadway.
 56. The portable rumble strip according to claim 55, wherein the filler is dispersed and embedded within a polymer composite matrix. 57-59. (canceled) 